INFLUENZA-INFECTED CELLS INCREASE LEVOFLOXACIN TOLERANCE OF STREPTOCOCCUS PNEUMONIAE

HERNANDEZ MORFA, MIRELYS; NICOLAS REINOSO VIZCAINO; NADIA B. OLIVERO; VICTORIA E. ZAPPIA; CORTES, PAULO; JAIME, ANDREA; ECHENIQUE J

Córdoba

Congreso; Reuniòn Anuel de la Sociedad Argentina de Microbiologia General; 2022

SAMIGE

Streptococcus pneumoniae is a major bacterial pathogen that usually colonizes the upper respiratory tract and causes pneumonia, bacteremia, and meningitis in humans. Pneumococcal infections are usually treated with beta-lactams and fluoroquinolones (FQs), but FQ resistance has been reported in this pathogen. In our lab, we have reported that host cell oxidative stress induces FQ tolerance, an unusual ability to tolerate the antibiotic effects. We have also demonstrated that intracellular survival of S. pneumoniae increases in host cells that are coinfected with the influenza A virus (IAV), and M2 a viral inhibitor of the autophagosome/lysosome fusion, mimics that phenotype. This synergistic mechanism depends on the SirRH two-component system of S. pneumoniae, which controls the expression of pneumococcal stress genes needed for survival in host cells. The main purpose of this work was to determine the impact of influenza A infection on the induction of FQ tolerance in intracellular S. pneumoniae. To study this phenomenon, A549 pneumocytes were coinfected with the IAV and S. pneumoniae, and we found a significant increase in the FQ tolerance compared to A549 cells infected only with pneumococci. We detected that the cytoplasmic ROS levels were increased in IAV-infected cells, indicating that the respiratory burst induced by IAV could be involved in this mechanism. When A549 cells were previously infected with IAV for 24 h, and then treated with NAC (a known ROS inhibitor) for 1 h before bacterial infection, we found a decrease in FQ tolerance of S. pneumoniae. To analyze the putative contribution of autophagy in the IAV-induced FQ tolerance in host cells, we coinfected MEF and MEF-atg5-KO (deficient in autophagy) cells with IAV and S. pneumoniae. In coinfected MEF cells we observed a similar FQ tolerance level to that observed in A549 cells, however, in MEF-atg5-KO we observed a decreased FQ tolerance. Altogether, these results suggest that FQ tolerance develops in coinfected cells in a ROS-dependent manner and this phenomenon occurs only in autophagy-proficient cells. Our findings in S. pneumoniae FQ tolerance acquisition are clinically relevant as it may cause complications in the antimicrobial treatment of pneumococcal infections.